Game crashes when /test verify-ing a test instance with max_attempts greater than 1

The bug

When you run a test instance via /test verify, and if the test instance has the max_attempts field of 2 or above, the game crashes.

Steps to reproduce

1. Create a superflat world with the attached data pack installed
2. Run

   /test verify test:1

   The game crashes after a short period of time.